1. Field of the Invention
The present invention relates to a development apparatus used for image forming apparatuses such as a copy machine, a printer, a facsimile, a multi-functional machine of them and the like that use an electro-photographic system and to an image forming apparatus that includes the development apparatus, more particularly, to a development apparatus that is able to cool a drive portion; and an image forming apparatus that includes the development apparatus.
2. Description of the Related Art
In image forming apparatuses such as a copy machine, a printer and the like, developers are stirred by a stir member in a developer container that stores the developers; the stirred developers are carried from the stir member to a development member; and the developers carried on the development member are formed into a thin layer by a blade; thereafter, the developers are supplied to an image carrier. As described above, in a development process in which a electrostatic latent image on the image carrier is formed into a visible image, heat is generated by friction between the developers due to the stirring, friction due to contact between the developers and the blade, and further slide friction due to the rotation driving of the stir member and the development member and the like, so that the temperature of the development apparatus increases
If the temperature of the development apparatus increases, the developers increase in temperature and are likely to deteriorate in performance; besides, fluidity of the developers deteriorate in the developer container and the developers are attracted to the blade and the development member, so that there is a risk that uneven development occurs and the development performance deteriorates.
As a measure against this, for example, there is a development apparatus in which a plurality of cooling fans are formed on a bottom surface of a development container that stores developers; and a heat sink is composed of the cooling fans. According to such a development apparatus, heat in the development container generated by the stirring of the developers and the contact between the developers and the blade is radiated by the heat sink to outside of the development apparatus.
As causes of the temperature increase of the development apparatus, besides the stirring of the developers in the development apparatus and the contact between the developers and the blade, there are the slide friction between the rotation shafts of the stir member and development member and their bearings, and the friction and the like of drive portions such as the friction of drive gears for rotating the stir member and development member, which generate heat. In recent years, because of high-speed image forming apparatuses, the rotation speed of the stir member and the development member becomes high, and the heat generation at their drive portions further increases the temperature of the development apparatus. However, in the above development apparatus, it is hard to curb the temperature increase due to the heat generation at the drive members of the development member and the stir member.